126 lines
2.3 KiB
ArmAsm
126 lines
2.3 KiB
ArmAsm
; FreeBSDで、死すコール番号を調べるには：/usr/include/sys/syscall.h
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; Linuxで、死すコール番号を調べるには：/usr/include/asm-generic/unistd.h
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; 下記のコードはFreeBSD向けの物です。
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bits 64
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default rel
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section .data
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section .rodata
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outfile db "output.ppm", 0
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hdr db "P6", 10, "960 540", 10, "255", 10
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err db "開くに失敗", 10
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errlen equ $-err
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suc db "画像を「output.ppm」に出力しました。", 10
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suclen equ $-suc
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w equ 960
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h equ 540
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section .bss
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buf resb 960*540*3
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section .text
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global _start
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_start:
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mov rax, 5 ; sys_openat
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lea rdi, [outfile]
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mov rsi, 0x100601 ; 0x100601 = 0001 0000 0000 0110 0000 0001 = 1048576 + 1024 + 512 + 1 = 1050113
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; O_WRONLY = 0x0001
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; O_CREAT = 0x0200
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; O_TRUNC = 0x0400
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; O_CLOEXEC = 0x010000
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; /usr/include/sys/fcntl.h
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mov rdx, 0o666 ; chmod 666
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syscall
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test rax, rax
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js error ; エラーがあれば
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mov r15, rax ; ファイルディスクリプターをrbxに保存
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; ヘッダーの書き込み
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mov eax, 4 ; sys_write
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mov rdi, r15 ; fd
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lea rsi, [hdr]
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mov rdx, 18
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syscall
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; チェッカーボードループ
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lea rdi, [buf]
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mov rcx, h
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yloop:
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mov r8d, w
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xloop:
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; (x/60 + y/60) % 2の計算
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mov eax, r8d
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xor edx, edx
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mov ebx, 60
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div ebx ; eax = x/60
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push rax
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mov eax, ecx
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xor edx, edx
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div ebx ; eax = y/60
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pop rdx
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add eax, edx ; x/60 + y/60
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and al, 1 ; % 2
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jz .black
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mov al, 0
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stosb ; R
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mov al, 0xFF
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stosb ; G
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mov al, 0
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stosb ; B
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jmp .next
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.black:
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xor eax, eax
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stosb
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stosb
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stosb
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.next:
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dec r8d
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jnz xloop
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loop yloop ; dec rcx, jnz yloop
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; ピクセルデータの書き込み
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mov eax, 4
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mov rdi, r15
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lea rsi, [buf]
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mov edx, 960*540*3
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syscall
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mov rax, 4
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mov rdi, 1
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lea rsi, [suc]
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mov rdx, suclen
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syscall
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close:
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mov rax, 6 ; sys_close
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mov rdi, r15
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syscall
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end:
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mov eax, 1 ; sys_exit
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xor edi, edi
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syscall
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error:
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mov rax, 4
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mov rdi, 2 ; stderr
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lea rsi, [err]
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mov rdx, errlen
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syscall
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mov rax, 1
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mov rdi, 1
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syscall
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